A runoff appeared likely in the GOP Senate primary between six-term incumbent Thad Cochran and tea party challenger state Sen. Chris McDaniel on Tuesday night

A runoff appeared likely in the GOP Senate primary between six-term incumbent Thad Cochran and tea party challenger state Sen. Chris McDaniel on Tuesday night, with the race tight, neither at over 50 percent and a little-known third candidate, Thomas Carey, tracking just under 2 percent.

McDaniel and Cochran swapped leads as results came in. With 97 percent of precincts in, unofficial results showed McDaniel leading 49.5 percent, or 147,451 votes, to Cochran's 49 percent or 146,071 votes. To avoid a runoff, a candidate must receive more than 50 percent. A runoff would be held on June 24.

Cochran had not spoken at his rally in Jackson as of presstime. McDaniel addressed his crowd at about 11:30 p.m.

"This is a historic moment in this state's history," McDaniel said. "But our fight is not over." He said there were still some votes uncounted and "we'll probably know tomorrow."

Cochran, facing his first serious challenge to re-election since 1984, had last year been an odds-on favorite, but McDaniel has crisscrossed the state campaigning hard and tapped into anti-Washington, anti-incumbent sentiment.

McDaniel on Tuesday won the key battleground of DeSoto County handily, 65 percent to 35 percent, and pulled an upset in Jackson County, in Cochran's Coast stronghold, winning there 49.5 percent to Cochran's 47.6 percent.

Cochran carried Madison and Harrison counties, Rankin County appeared to be a push, although many votes remained out late.

Turnout ended up better than early indications and estimates, at about 300,000 for the GOP primary, around the same number as the heated 2012 presidential primary.

The candidates' enthusiasm waxed and waned as numbers came in and leads swapped through the night.

Jane Crump, 60, of Schlater was at Cochran's first victory party in Jackson in 1978. She's been campaigning for him ever since and was at his election-night gathering in Jackson on Tuesday.

"He's absolutely dedicated to the state of Mississippi," Crump said. "He's the ultimate statesman ... He's the man for the job. I can't imagine him not being my senator."

McDaniel supporter Ross Tew of Laurel said he aligned himself with McDaniel because their ideologies tend to be the same.

"The main reason is the fact that he's such a staunch conservative," said Tew. "His views are my views, where I'm not into bringing home the pork."

Tew said McDaniel's standing as a God-fearing man also influenced his decision to cast his ballot for the state senator.

For some, the prospect of three more weeks of what has been one of the most bitter, negative races in state history is daunting.

"What it will do is give more time for the nursing home scandal to play out, more outside money will come in, and more negative ads," said John Bruce, chairman of the Ole Miss Political Science Department. "That's not good for anybody."

McDaniel, 42, has capitalized on anti-Washington sentiment and tea party fervor, both of which have been growing in Mississippi.

Tea party groups on the national level provided his cause much needed money and advertising, and local groups provided foot soldiers and social media warriors.

He painted Cochran as too "liberal," too old, and as a Washington insider out of touch with a more conservative Mississippi.

Cochran, 76, ran in part on his record in Washington and the potential for him to regain his chairmanship of the powerful Appropriations Committee if the GOP retakes the Senate. But his long, storied record of bringing home the federal bacon had also become his cross to bear.

The race was seen as the tea party's best, then later only, chance to unseat a high-profile incumbent U.S. senator. This brought an influx of outside super PAC spending for both candidates and a flood of negative campaigning and advertisements.

It's unclear what role a late-race scandal in mid- to late-May played on Tuesday. Four McDaniel supporters, including a state tea party executive, were charged with felonies for allegedly taking photos of Cochran's bedridden wife in a nursing home for use in a political hit-piece video.

The Cochran campaign attempted to capitalize on the incident, running ads linking McDaniel to it. McDaniel, who has denied any involvement, countered with ads calling Cochran "shameless" for trying to score political points.

Bruce speculated some potential voters were "feeling nauseous" from being bombarded by negative ads, robocalls and news of scandal and didn't bother.

Cochran's campaign raised about $3.6 million for the race; McDaniel's $1.2 million. But outside interests pumped in nearly $8 million, including $4.5 million for McDaniel and $3.2 million for Cochran.

The race has shown the Mississippi GOP is a party divided, between its establishment and the tea party, and its leaders say they plan to work to get everybody back in the tent.

"It's more than just the usual singular hurt feelings," said state GOP Chairman Joe Nosef. "We have to get a broader range of people brought back into the fold … I do worry about a big swath of the Republican Party labeled as establishment and vilified. I don't think establishment is a dirty word. We ought to be patting folks on the back for what they've done. This task will be as challenging as it ever has been."

As the Mississippi Republican Party seeks to heal wounds over the bitter battle between the tea party and establishment, Nosef said he looks to Gov. Phil Bryant — who has a foot in each camp although he endorsed Cochran — to help unify the party.

"The governor has managed to maintain his popularity with those people who identify as Republican establishment or whatever you want to call it, Libertarian, conservative or tea party Republican," Nosef said. "Phil has all their support, and he will be very instrumental."